In-situ electron channeling contrast imaging of cyclic deformation mechanisms in CrCoNi medium-entropy alloy

In this paper, we report deformable blend thin films of polymer semiconductors with PDPPTT (p-type) and N2200 (n-type) as the examples by using the hydrogenated polyisoprene (H-PIP) as the newly developed elastomer. As compared to the respective blends with other elastomers, the blends with H-PIP bear lower elastic moduli and higher crack on-set strains, and in particular exhibit remarkably stable semiconducting performance under large and cyclic mechanical deformations. This aligns with the observation that the assembly structures of polymer semiconductors are stable within the H-PIP matrix based on AFM and GIWAXS characterizations. This exceptional performance is attributed to the unique structure of H-PIP, which is solely composed of mobile aliphatic-hydrocarbon chains without chemical/physical crosslinks. This enables the blend thin films with H-PIP to follow the mechanical deformations of the substrate without generating internal stress and affecting the interconnected assembly networks of the polymer semiconductor, thus leading to stable semiconducting performance.

Ear-based electroencephalography (ear EEG) has emerged as a promising alternative to traditional scalp EEG due to its unobtrusiveness, quick and user-friendly application, as well as stable electrode placement enabled by the ear canal's specific anatomical structure. However, reliable signal acquisition in such wearable systems requires electrodes that sustain robust skin contact, mechanical durability, and electrochemical stability under sweating, motion, and long-term use. Conventional ear electrodes, such as 3D-printed personal ear models with metal contacts, are conductive but rigid, gel-dependent, and logistically complex, resulting in poor skin–electrode interfaces, low signal quality and less practicality.Emerging ear electrodes integrating generic earplug and E-textile electrode stand out for breathability, conformability, robust connection with electronics and simplicity. However, conventional e-textiles rely on metallic coatings that are hydrophobic and prone to cracking and oxidation, resulting in overall unstable contact and compromised long-term signal fidelity which limit their application in wearable electronics. As a result, current devices still majorly depend on wet electrodes to achieve high-fidelity signal acquisition, which makes them slower to apply, unsuitable for long-term use and susceptible to performance degradation under dynamic or adverse conditions.To overcome these limitations, we present a PEDOT:PSS-functionalized, silver-coated textile electrode paired with a foam earplug substrate, engineered to improve conductivity, and enhance skin–electrode contact , thereby enabling gel-free application. The PEDOT:PSS layer also protects the metallic coating from cracking and oxidative degradation during motion, sweating, and repeated use, ensuring both electrochemical and mechanical robustness.A dip-coating method was used to coat PEDOT:PSS onto commercial Ag/nylon fabric (surface resistance ≤0.05 Ω/sq) following ethanol–acetone pretreatment to improve adhesion. To ensure uniform coating, the fabric squares were placed on a sponge, brushed evenly with PEDOT:PSS ink, and dried at 80 °C. Conductivity was enhanced by adding 4% DMSO to the raw PEDOT:PSS solution. Stainless-steel thread was interwoven to provide durable, solderless electrical connections. Surface resistance and cyclic deformation tests (twisting, bending, folding) were performed to evaluate electrical durability. Tensile tests assessed stretchability of the polymer-coated E-textile. Contact angle analysis and in-ear skin–electrode impedance were used to evaluate wettability and interface stability with the skin. Long-term reliability was evaluated by monitoring oxidation in an 80 °C oven, assessing 1-hour in-ear impedance drift, and examining consistency after repeated reattachment. A tensile load test, with rupture location (junction vs. wire) recorded, further assessed mechanical robustness, while surface roughness and brittleness were analyzed to characterize coating integrity. Long-term stability was also validated by consistent in-ear impedance over 1 hour and reproducibility after repeated attachment cycles and human motion. Finally, in-ear EEG recordings showed alpha modulation when benchmarked against wet electrodes to validate signal fidelity under dynamic conditions.With 1.5% PEDOT:PSS, surface resistance decreased by 42.9% compared to bare textiles, and fractional resistance remained stable through 20 cycles of twisting, bending, and folding, confirming robust electrical durability. Strain tolerance increased by 18% in tensile tests, indicating improved mechanical resilience. Contact angle decreased by 76.3%, and in-ear skin–electrode impedance dropped by over 50%, demonstrating enhanced wettability and interface stability. Oxidation tests confirmed protection of the metallic substrate, while rupture testing showed strong interface connections. Surface roughness and brittleness analyses further indicated smoother, more stable coating morphology. Long-term stability was validated by consistent in-ear impedance over 1 hour and reproducibility after repeated attachment cycles and human motion. Compared with wet in-ear electrodes, PEDOT:PSS-functionalized electrodes exhibited lower impedance drift, higher SNR, and clear alpha modulation in in-ear EEG recordings, confirming reliable signal fidelity under dynamic conditions.As a conductive polymer with mixed ionic–electronic transport, PEDOT:PSS reduces interfacial impedance and increases surface wettability, thereby improving skin–electrode coupling without the need for gels. Its conformal coating also distributes strain more evenly across the textile fibers, explaining the stable resistance under deformation and the enhanced strain tolerance observed in tensile testing. Additionally, the polymer layer forms a protective barrier that protects the underlying metallic coating from cracking and oxidation, which underlies the stable performance across reattachments and over time. Most critically, in-ear recordings showed clear alpha modulation with higher SNR and lower drift than wet in-ear electrodes, demonstrating that the material-level improvements translate into enhanced functional performance.Leveraging the inherent advantages of conductive, conformable, and breathable e-textiles, the PEDOT:PSS coating further reduces impedance, improves electrode–skin contact and wettability, enhances mechanical and electrochemical stability, and ensures long-term reliability, establishing a robust and practical platform for wearable EEG monitoring. Figure 1

Numerical analysis of monotonic and cyclic long-term deformations in pile tests from the TU Darmstadt blind prediction contest using an HCA model

Low cycle fatigue behavior and cyclic deformation mechanism of 2195 Al-Li alloy at low temperatures

A reliable design of dynamically loaded components requires a thorough understanding of the fatigue properties of metallic materials. This article focuses on extending conventional methods to include non-destructive testing (NDT)-based methods, which enable a process-oriented evaluation of fatigue behaviour instead of a lifetime driven approach. The use of NDT-generated data to describe cyclic deformation curves not only enables a significant increase in information, but also a generation of virtual S-N curves with a significantly reduced number of specimens. Therefore, synergies between the two disciplines of NDT-based and conventional destructive materials testing are used to enable a better understanding of ongoing processes. The main focus lies on the development of thermographic evaluation approaches, whereby further methods such as resistance measurements are used additionally. The test materials are two unalloyed steels of grade SAE 1020 and SAE 1045, as well as the low-alloyed 20MnMoNi5-5 steel.

ABSTRACT The present study investigates the effect of microstructure evolution, including grain refinement and grain orientation, on the surface residual stresses of friction stir processed (FSP) Al6061 alloy. Grain rotation, dynamic recrystallization (DRX), and grain boundary migration are all induced by the FSP process, which results in notable microstructural alterations. According to EBSD analysis, the original S-rolling texture changes into Brass and Goss textures while grain size decreases and high-angle grain boundaries (HABs) increase. The residual stress distribution measured at various depths is correlated with these microstructural alterations, because of the severe plastic deformation and thermal cycles after FSP, residual stresses close to the surface become extremely compressive, reaching a maximum negative value of −564 MPa at 500 µm depth. Residual stresses change from compressive to tensile at deeper depths; at 2000µm and reaches 375 MPa. The relationship between residual stress redistribution and microstructural evolution shows that stable textures and finer grains lead to a more advantageous residual stress state. FSP significantly reduced wear depth and coefficient of friction by fine-tuning the grain structure and increasing the high-angle grain boundary content. Following FSP, SEM images revealed smoother surfaces with minimal damage.

Gallium-based liquid metals (LMs) are considered promising electrodes for supercapacitors owing to their metallic conductivity and high deformability. LMs can form nanoparticles via ultrasonication and can be further transformed into rod morphologies via hydrothermal treatment. Remarkably, LM rods exhibit a larger surface area than particles, allowing them to be highly decorated with different metals via galvanic replacement. In this study, a novel electrode is introduced, shape-transformed liquid metal rods decorated with NiCo2O4 nanoneedles anchored on activated carbon. Electrodes with hierarchical structures enhanced the pseudocapacitive performance in an alkaline electrolyte (1.0m KOH), achieving a high specific capacitance of 749.6 F g-1 at 1 A g-1. Owing to the deformability of the LM electrodes as well as the use of LM current collectors, the devices are endowed to be fully soft and exhibited mechanical and electrochemical stability even after cycles of deformation. When assembled into an asymmetric soft supercapacitor with activated carbon as a cathode, the device delivered a specific capacitance of 45 F g-1 at 2 A g-1 and retained 96% of its initial capacitance even after 10 000 galvanostatic charge-discharge (GCD) cycles and after 1 000 mechanical bending cycles with 50% compression, and stretching cycles with 30% elongation.

Experimental investigation on GFRP-reinforced UHPECC beams subjected to various cyclic deformation histories

Multiple-mechanism and microstructure-based crystal plasticity simulation of cyclic deformation in TRIP-assisted duplex stainless steels

This study employs a combination of Vlasov’s thin-walled beam theory and a multi-variable power series approach to analyze the elastic stability of mono-symmetric box girders, a class of thin-walled structural elements widely used in bridge engineering, subjected to eccentric transverse loading. The primary objective is to investigate the discrepancy between the shear center and the center of gravity, which induces complex coupled deformation modes, particularly flexural and distortional effects. Using Varbanov’s modified generalized displacement functions, the governing differential equation of equilibrium were derived based on section properties evaluated at the pole and shear center, through a unit displacement approach. Essential cross-sectional parameters were obtained using enhanced product integrals (diagram multiplications). Given the complexity of the governing equation and boundary conditions, exact closed-form solutions were not attainable. To address this, three analytical methods, power series, trigonometric series, and Taylor-Maclaurin series, were applied to solve the reduced equations, enabling a comprehensive evaluation of flexural and distortional behaviors. Among these, the power series method proved most effective, accurately capturing the multi-variable interactions required to model realistic deformation patterns. Under eccentric loading, maximum flexural deformation occurred at 10 and 40 meters, while distortional deformation peaked at 40 meters and diminished near 45 meters. The Taylor-Maclaurin series showed maximum flexural deformation at 30 meters and distortional deformation at 9 meters. The trigonometric series revealed cyclic deformation patterns indicative of fluctuating load effects but lacked the precision needed for complex geometries. This study addresses a notable gap in the literature by providing a robust analytical framework for mono-symmetric girders and emphasizes the importance of advanced multi-variable analytical techniques in structural design and engineering education.

Rheumatoid Arthritis (RA) and Osteoarthritis (OA) are among the most impactful musculoskeletal disorders causing articular cartilage degradation, ultimately leading to loss of the joint functionality. Matrix-assisted Autologous Chondrocytes Implantation (MACI) is one of the most promising reconstructive techniques to treat chondral defects (CDs). MACI relies on a matrix cellularized with autologous chondrocytes implanted directly onto cartilage defects. Despite MACI's effectiveness, post-surgery rehabilitation remains a challenge, as it fails to induce the optimal mechanobiology necessary for an effective cartilage regeneration. Additionally, there is a significant patient-to-patient variability and the local loads occurring during rehabilitation might consequently vary greatly. We propose a personalized approach focused on the delivery local pro-regenerative mechanobiological cues to dramatically improve the cartilage restoration after MACI.We developed an innovative scaffold to be used as matrix in MACI, capable to enhance the cartilage repair by delivering in situ controlled, and personalized, mechanical cues triggering pro-regenerative cellular responses to embedded human articular chondrocytes (hACs). The scaffold relies on an electrospun matrix made of aligned fibers composed of PVDF-TrFE, a piezoelectric polymer, enriched with ferromagnetic Fe3O4 nanoparticles capable to confer magnetic properties to the scaffold. MNPs were simultaneously dispersed in the polymeric solution, and microfibers were collected onto a high-speed rotating collector to obtain an aligned micropattern, capable to give mechanical anisotropy to the scaffold. After cellularization with hACs, we subjected the scaffold to daily magnetic stimulation up to 14 days.The scaffold was highly responsive to external magnetic stimuli. In addition, hACs produced a type II collagen-rich extracellular matrix when cultured within the scaffolds subjected to magnetic stimulation. Remarkably, we observed an increase of cell viability, and of type II/type X collagen ratio.Our scaffold was able to provide pro-regenerative cues to hACs after mechanical cyclic deformations induced by repeated magnetic stimulations. Such an approach paves the way to an effective, and definitive therapeutic procedure for the treatment of chondral defects.

Variation of Low Cycle Fatigue Life in TA5 Alloy as a Function of Different Cyclic Deformation Mechanisms

Abstract Most theories and applications of elasticity rely on an energy function that depends on the strains from which the stresses can be derived. This is the traditional setting of Green elasticity, also known as hyper-elasticity. However, in its original form the theory of elasticity does not assume the existence of a strain energy function. In this case, called Cauchy elasticity, stresses are directly related to the strains. Since the emergence of modern elasticity in the 1940s, research on Cauchy elasticity has been relatively limited. One possible reason for this is that for Cauchy materials, the net work performed by stress along a closed path in the strain space may be nonzero. Therefore, such materials may require access to both energy sources and sinks. This characteristic has led some mechanicians to question the viability of Cauchy elasticity as a physically plausible theory of elasticity. In this paper, motivated by its relevance to recent applications, such as the modeling of active solids, we revisit Cauchy elasticity in a modern form. First, we show that in the general theory of anisotropic Cauchy elasticity, stress can be expressed in terms of six functions, that we call Edelen-Darboux potentials. For isotropic Cauchy materials, this number reduces to three, while for incompressible isotropic Cauchy elasticity, only two such potentials are required. Second, we show that in Cauchy elasticity, the link between balance laws and symmetries is lost, in general, since Noether’s theorem does not apply. In particular, we show that, unlike hyperleasticity, objectivity is not equivalent to the balance of angular momentum. Third, we formulate the balance laws of Cauchy elasticity covariantly and derive a generalized Doyle–Ericksen formula. Fourth, the material symmetry and work theorems of Cauchy elasticity are revisited, based on the stress-work 1-form that emerges as a fundamental quantity in Cauchy elasticity. The stress-work 1-form allows for a classification via Darboux’s theorem that leads to a classification of Cauchy elastic solids based on their generalized energy functions. Fifth, we discuss the relevance of Carathéodory’s theorem on accessibility property of Pfaffian equations. Sixth, we show that Cauchy elasticity has an intrinsic geometric hystresis, which is the net work of stress in cyclic deformations. If the orientation of a cyclic deformation is reversed, the sign of the net work of stress changes, from which we conclude that stress in Cauchy elasticity is neither dissipative nor conservative. Seventh, we establish connections between Cauchy elasticity and the existing constitutive equations for active solids. Eighth, linear anisotropic Cauchy elasticity is examined in detail, and simple displacement-control loadings are proposed for each symmetry class to characterize the corresponding antisymmetric elastic constants. Ninth, we discuss both isotropic and anisotropic Cauchy anelasticity and show that the existing solutions for stress fields of distributed eigenstrains (and particularly defects) in hyperelastic solids can be readily extended to Cauchy elasticity. Tenth, we introduce Cosserat–Cauchy materials and demonstrate that an anisotropic three-dimensional Cosserat–Cauchy elastic solid has at most twenty four generalized energy functions.

Deformable all-solid-state energy storage systems are grabbing significant interest; however, the simultaneous acquisition of high stability alongside high power and energy densities for user-oriented portable electronics remains a daunting challenge. Thus, hybridizing battery and capacitor materials offers a prospective strategy toward efficiently bridging the performance gap between high-energy batteries and high-power supercapacitors. In this work, an all-solid-state deformable hybrid supercapacitor (ADHS) utilizing interfacially coupled in situ carbon-doped zinc cobaltite/MXene (MCZ) as anode and porous self-phosphorus-doped bio-carbon (TAC) derived from Averrhoa carambola leaves as the cathode is presented. The anode delivers high energy via battery-type storage, while the porous cathode ensures stable, high-power output over a broad potential window. The ADHS exhibits a specific capacitance of 124.13 F g-1, energy density of 119.16Wh kg-1, and power density of 3139.53W kg-1, with 90.55% initial capacitance retention post 20000 cycles, outperforming or matching state-of-the-art storage devices. Furthermore, the device maintains electrochemical stability under 100 deformation cycles and various twisting angles, highlighting its promise for next-generation energy storage applications.

Abstract This study explores the cyclic elastoplastic deformation behavior of an Fe–Mn–Al–C alloy at room temperature by employing load-controlled nanoindentation with a Berkovich indenter, offering new insights into the competition between plastic and elastic energy. The dynamic nanoindentation tests were conducted with load ratios $$\left(R= {P}_\text{min}/{P}_\text{max}\right)$$ R = P min / P max ranging from 0 to 0.5 for 100 and 200 mN, considering 50, 300 and 500 loading cycles. Results revealed that at the maximum depth, the elastic (E e) and plastic (E p) energy remains constant, whereas the ability to absorb E p decreases by approximately 1.4 and the E e decreases by approximately 1.5 when R varies from 0 to 0.5. Additionally, the relationship between E e and E p is ~ 2 times regardless of the load or number of load cycles. The occurrence of pop-ins at low loads suggests potential interactions between dislocations and twins, given the austenitic nature of the alloy with a low stacking fault energy (SFE). Creep behavior was analyzed at loads ranging from 1 to 10 mN with a holding time of 30 seconds. The creep rate increases with increasing load and holding time, suggesting that at the macroscopic scale, the strain rate affects the strain hardening rate.

Extreme cold weather seriously harms human thermoregulatory system, necessitating high-performance insulating garments to maintain body temperature. However, as the core insulating layer, advanced fibrous materials always struggle to balance mechanical properties and thermal insulation, resulting in their inability to meet the demands for both washing resistance and personal protection. Herein, inspired by the natural spring-like structures of cucumber tendrils, a superelastic and washable micro/nanofibrous sponge (MNFS) based on biomimetic helical fibers is directly prepared utilizing multiple-jet electrospinning technology for high-performance thermal insulation. By regulating the conductivity of polyvinylidene fluoride solution, multiple-jet ejection and multiple-stage whipping of jets are achieved, and further control of phase separation rates enables the rapid solidification of jets to form spring-like helical fibers, which are directly entangled to assemble MNFS. The resulting MNFS exhibits superelasticity that can withstand large tensile strain (200%), 1000 cyclic tensile or compression deformations, and retain good resilience even in liquid nitrogen (- 196°C). Furthermore, the MNFS shows efficient thermal insulation with low thermal conductivity (24.85 mWm-1K-1), close to the value of dry air, and remains structural stability even after cyclic washing. This work offers new possibilities for advanced fibrous sponges in transportation, environmental, and energy applications.

The eruption cycle of a volcano is controlled by the subsurface migration and storage of magma. The specific characteristics of the magma migration and spatial distribution of material properties produce a specific deformation signature on the Earth’s surface. Inverse analyses of geodetic data are used to optimize characteristic geometric and mechanical parameters of the volcanic system and hence provide information on the subsurface magmatic system. This study uses interferometric synthetic aperture radar data from a 1997 co- and post-eruptive interval for Okmok volcano to estimate the location of the magma reservoir and constrain finite element-based viscosity models of a thermally-weakened viscoelastic rind surrounding the reservoir. For the first time, approximately 10 years of pre-and post-eruption interferometric synthetic aperture radar data are analyzed to recover a magma reservoir pressurization history using both purely elastic and coupled elastic-viscoelastic models. The findings show that low viscosities surrounding the magma reservoir relax stresses rapidly enough to allow prediction of the more realistic viscoelastic pressurization histories to be calculated as a scaled version of the relatively simple but computationally efficient elastic models which allows for quick analysis of volcano hazards while maintaining fidelity to the actual physical system. This offers insights into how the shallow rheologic structure of magmatic systems can influence the predictions of transient deformation and estimates of the time-dependent magma budget.

Flexible sensors have emerged as essential components in next-generation technologies such as wearable electronics, smart healthcare, soft robotics, and human–machine interfaces, owing to their outstanding mechanical flexibility and multifunctional sensing capabilities. Despite significant advancements, challenges such as the trade-off between sensitivity and detection range, and poor signal stability under cyclic deformation remain unresolved. To overcome the aforementioned limitations, this work introduces a high-performance soft sensor featuring a dual-layered electrode system, comprising silver nanoparticles (AgNPs) and a composite of multi-walled carbon nanotubes (MWCNTs) with carbon black (CB), coupled with a laser-engraved crack-gradient microstructure. This structural strategy facilitates progressive crack formation under applied strain, thereby achieving enhanced sensitivity (1.56 kPa−1), broad operational bandwidth (50–600 Hz), fine frequency resolution (0.5 Hz), and a rapid signal response. The synergistic structure also improves signal repeatability, durability, and noise immunity. The sensor demonstrates strong applicability in health monitoring, motion tracking, and intelligent interfaces, offering a promising pathway for reliable, multifunctional sensing in wearable health monitoring, motion tracking, and soft robotic systems.

Osteoarthritis results in deterioration of articular cartilage, the soft tissue covering articulating surfaces of bones in joints like the knee and hip. Prior studies show that cyclical mechanical stimulation of articular cartilage results in synthesis of cartilage matrix, suggesting that therapeutic mechanical stimulation might be beneficial for cartilage repair in osteoarthritis. Several prior studies identify ion channels and cytoskeletal molecules as components of chondrocyte mechanotransduction. The pathways of central metabolism, glycolysis, the pentose phosphate pathway, and the tricarboxylic acid cycle, are necessary for producing non-essential amino acids that are needed for synthesizing matrix proteins for cartilage repair. However, it is currently unknown if and how levels of central metabolites change with applied mechanical stimulation of chondrocytes. Here, we show that applied cyclical shear and compressive deformations drive changes in multiple central metabolites. These results add to a rich picture of chondrocyte mechanotransduction including calcium signaling, ion channels, integrins, and cytoskeletal components. By finding compression- and shear-induced changes in central metabolites, these data support the potential for therapeutic mechanotransduction toward cartilage repair. Future studies may build on these results to understand the relationships between mechanical stimulation and chondrocyte central metabolism.